The present invention relates to a mounting structure for a chemical injection tube for geothermal wells utilized for power generation from geothermal energy and especially dominated by hot water with steam.
A considerable amount of alkaline earth metals are dissolved in geothermal fluids under high temperature and high pressure subterranean conditions. When the fluid flows up the well such alkaline metals tend to deposit onto the wall surface of the well as carbonates, which then become scale.
The scale causes insufficient fluid production due to its plugging effect and, in an extreme case, complete closing of the well may occur.
Furthermore, there would be a chance for hot water to contain salt deposits already in deep subsurface formations, depending upon the pressure, temperature, ion species and their concentration.
It is heretofore unknown to prevent such carbonates scale adhesion by providing a chemical injection tube in a geothermal well, except that some chemical injection methods are known for hot spring wells. However, the hot spring wells are generally so shallow as compared with geothermal steam wells (hereinafter called "geothermal well"), that liquid chemical injections are only made by manual operation of workers.
However, in the case of a much deeper geothermal well (1000 m or more), chemical injection by manual operation is not only more difficult but also very dangerous due to the blowing of high pressure hot steam.
According to the present invention a chemical injection tube is inserted at the well head into a deep well bore. The upper end the tube is fixed with a sealing flange and at its lower end, extending deeper than the flashing point of the geothermal fluid, the tube is submerged in the fluid.
Scale inhibiting chemicals are added at the upper end and injected directly into the geothermal fluid in the well bore through said tube.